Method to connect drill holes utilizing signalling devices

ABSTRACT

This is a method to connect two or more drill holes, such as drill holes at distances of 2,000 to 5,000 feet or more apart, for the purpose of producing soluble ores, such as sylvanite or carnallite, from thick, deep ore bodies or from thin, shallow ore bodies. The drill holes are connected utilizing a signal-sending device in an initial drill hole and a sigal-receiving device in a subsequent drill hole. A fluid is injected down one of the holes forcing the effluent from the other hole thus forming a mined-out corridor between the two holes. This procedure can then be repeated with subsequent, offset drill holes.

BACKGROUND OF THE INVENTION

This invention is in the field of recovery of soluble, evaporite ore bysolution mining between two or more drill holes. More particularly, itinvolves an efficient method to connect drill holes that recovers alarger proportion of the soluble ore in the ore body than previouslyrecovered by prior art. One basic method involving more than one hole isto drill two conventional, vertical holes into a soluble ore layer.Solution mining is employed in each drill hole creating cavities in theexisting ore body. Oil is then introduced into each cavity forming aninsoluble pad in the cavity's upper surface and forcing the rapidformation of a flattened cavity. The flattened cavities grow in sizeuntil they join together. The formation can then be mined by pumpingfresh water into one drill hole and removing saturated ore solution fromthe other drill hole. Using this method, both drill holes must becompleted for individual mining operations and the process to achievecoalescence is slow.

Another method is to drill two conventional, vertical holes spaced adistance apart from each other. One or both of the drill holes isfractured using a high pressure procedure frequently employed by thepetroleum industry. 1f the fracture procedure opens a passageway betweenthe two drill holes, water can then be pumped down one drill hole andsaturated ore solution can be removed from the other drill hole. ln thismethod there is no way to control the direction of fracture. Therefore,to insure success, the holes must be drilled closely together. Even ifthe holes are drilled closely enough together to connect by fracturing,the resulting cavity formation is small and the total saturated orerecovery is diminished.

Still another method is to locate the positions at which two holesspaced a distance apart from each other can be drilled down to thesoluble ore body. One of the holes is drilled vertically(conventionally). The other hole is drilled from a point on the surfaceat a selected distance. This hole is deflected as it is drilled in thedirection of the conventional hole. The base of the deflected drill holethen approaches the base of the conventional drill hole. The soluble orebody is fractured by the force from a liquid under high pressure, suchas a saturated salt solution, injected down one or both drill holes toobtain a fissure tying together the bases of the two drill holes. If thefracture attempt is unsuccessful, the deflected hole is drilled furthertoward the bottom of the conventional hole. One or both of the drillholes is again fractured to obtain interconnection. If interconnectionis not achieved, the drill holes are individually solution mined to formcavities. When the cavities grow until they join, the soluble ore bodyis mined by pumping fresh water down one drill hole thereby forcingsaturated ore solution out of the other drill hole.

Another disadvantage of these previous methods of connecting two holesis that more holes must be drilled to extract soluble ore from a givenarea than in the present invention, thereby adversely affecting theeconomics of the procedure. The present invention results in fewer drillholes, more accurate connection of said drill holes and ore recoveryfrom a larger area of a mineral-bearing stratum resulting in lower,overall production costs than the prior art.

SUMMARY OF THE INVENTION

The present invention is a method to economically solution mine thick,deep, soluble ore bodies or thin, shallow ore bodies from two or moredrill holes located at the surface a distance of 2,000 to 5,000 feet ormore apart. The depths of these soluble ore bodies are normally too farbeneath the surface to be mined conventionally, such as by sinking ashaft and sending men underground. If the formation is at a shallowdepth, the ore zone may be too thin to mine conventionally.

First, the upper portion of the initial hole is drilled vertically(conventionally) to the top of the evaporite sequence. The lower portionof the drill hole is then deflected in the direction of the strike ofthe ore zone with the use of a deflecting motor. When the drill bitreaches the lower part of the closest, clastic layer overlying the orezone, casing is run and cemented. A smaller drill bit and deflectingmotor that fit the smaller size of the casing are attached to the drillpipe and deflected drilling continues to carry the drill hole to ahorizontal position and reach a distance of an additional 1,000 to 5,000feet or more. A signal-sending device is then placed at the end of thefirst drill hole.

The location of the second drill hole is surveyed in on the surface at apoint that is precisely vertical from the signal-sending device in thefirst drill hole. The second hole is drilled vertically(conventionally). When the top of the evaporite sequence is reached, thedrill pipe is pulled in order to place a signal-receiving device in anon-magnetic section of drill pipe immediately behind the drill sub andbit. The drill pipe is placed back in the second drill hole whereuponthe signalling device in this second drill hole picks up the signal fromthe signalling device in the first drill hole. Monitoring-while-drillinginstrumentation guides the drill bit to the base if the closest, clasticlayer directly above the signal-sending device in the first drill hole.The second drill hole is cased to total depth and cemented. A smallerdrill bit is attached to accommodate the smaller size of the cased hole,and further drilling results in the connection of the two holes. Ifinterconnection is not achieved, the two drill holes are joined bydissolving a cavity in the ore zone at the base of the second drill holeto reach the base of the first drill hole.

The soluble ore is then mined between the two drill holes by injectingwater down one drill hole and withdrawing saturated ore solution fromthe other drill hole. To insure a symmetrical cavity in the ore body,the direction of the influent is periodically reversed between the twodrill holes. The size of the cavity can be controlled by adjusting thelevel of an in-place petroleum blanket or nitrogen or normal air padwhich is also useful in preventing the upward dissolution of any halitelocated between the ore zone and the overlying, insoluble clastic layer.The position of the pad or blanket is maintained deep in the ore zoneduring the early stages of the dissolution process so that the desiredwidth of the cavity can be attained and controlled.

Should dissolution of ore need to be accelerated for any reason such asto control cavity width, the brine level in the cavity can be adjustedfor a short interval to a point below the roof of the ore body andunsaturated water can be run along the saturated, fluid surface beneaththe exposed ore roof. The brine can then be returned to its originallevel. This method can also be utilized to selectively dislodge smallportions of interbedded sodium chloride crystals particularly whenmining lower grade sylvinite ore. As the sodium chloride is dislodgedand falls to the floor of the cavity, the potassium and/or magnesiumchloride to sodium chloride ratio can be improved in the effluent.

A third hole can be located at a point that will allow the previouscorridor to be extended or it can be positioned at a right angle to thecavity created in the ore body by the first two drill holes. Whenconnection is made to a third drill hole and a corridor is established,the dissolution process can continue to mine out a triangular area amongthe three drill holes. If the third drill hole is located up-dip fromthe first two drill holes, the third drill hole becomes the influentdrill hole. If the third drill hole is located down-dip from theoriginal, two drill holes, the third drill hole becomes the effluent orproduction drill hole. This procedure is necessary due to the increaseof specific gravity of the brine as it becomes more saturated with thedissolved ore. A subsequent hole can be located and drilled to eitherfurther extend the previous corridor or to create a second triangle andthereupon complete a square or rectangular shaped cavity in the orezone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a solution mine in an intermediatestage according to the process of this invention. FIG. 2 is a plan viewof a solution mine showing the expansion of this method according to theprocess of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing shown in FIG. 1, numeral 1 designates aninitial, vertical hole drilled to the top of evaporite sequence 5. Adeflecting motor begins to turn the lower portion of the drill holeuntil the base of the clastic layer 7 closest to the underlying,objective soluble ore zone 8 is reached. Casing 9 is set from thesurface to the base of the clastic layer 7 and cemented 10, reducing thesize of the drill hole 1. A smaller deflecting motor is attached to thedrill pipe 15 and deflected drilling continues in ore zone 8 until drillhole 1 is in a horizontal position at or near point 6. This extendedreach procedure is followed by pumping air or water as a circulationfluid through the drill pipe 15 and pushing the signal-sending device 11to or near the end of the first drill hole 1. The location of the seconddrill hole 2 is then surveyed in on the surface at a point directlyabove the signal-sending device 11. This second hole 2 is drilled to apoint at which communication with the in-place, signal-sending device 11becomes possible. The signal-receiving device 12 is then placed in anon-magnetic pipe 14 and attached to the drill pipe 15 behind the drillbit 13 or optional drilling sub 16. The drill bit 13, guided toward thesignal-sending device 11 by the signal-receiving device 12, is steeredby monitoring-while-drilling equipment which provides a surface read-outof the location of the drill bit 13 so that directional adjustments canbe made. Once a point near the base of the clastic layer 7 overlying orezone 8 is reached, casing 9a is run and cemented 10a. The second drillhole 2 is then drilled to the base of ore zone 8 and accurately connectswith the first hole 1. When interconnection is achieved between thefirst hole 1 and the second hole 2, injection of the influent commencesat one of the holes and the effluent from ore zone 8 is recovered fromthe other hole. To control the size of the cavity, the direction of theinfluent is alternated between the two holes. Further, this "u-shaped"system of fluid input or influent and brine production output oreffluent is not restricted to level ore zones but can be achieved by thesame connecting procedure in dipping ore zones and/or expanded toinclude other, underlying ore zones; i.e., to produce from two zonesseparately or concurrently. After mining out an initial cavity orcorridor 17 between two holes 1,2 as seen in FIG. 2, the procedure canbe repeated to mine between two additional drill holes or to connect anew drill hole located at a right angle to the corridor 17 in ore zone 8created by the first two holes 1,2 as follows. Drill and case a thirdhole 3, mine out the second corridor 18, mine out the first triangle 19,drill a fourth hole 4, mine out corridor 20 and finally, mine out thesecond triangle 21 to complete a square or rectangular shaped cavity.

The disclosure of the invention described hereinabove represents thepreferred embodiments of the invention; however, variations thereof, inthe form, sequence of holes, construction and arrangement of the variouscomponents thereof and the modified application of the invention arepossible without departing from the spirit and scope of the claimsherein.

What is claimed is:
 1. A method of establishing accurate communication between drill holes in deep, thick or shallow, thin soluble ore bodies comprising the following steps:a. drilling an initial hole to the top of the closest, overlying evaporite sequence to the ore zone, said hole then being deflected horizontally to reach the soluble ore zone; b. drilling to a point at a distance of 1000 to 5000 feet or more from the point of deflection; c. pushing a signal-sending device to the base of the said initial hole whereupon the position of the said signal-sending device can be surveyed in to establish the location of a second drill hole; d. drilling a second hole to the position of the aforementioned signal-sending device in the initial hole utilizing a signal-receiving device positioned in the drilling apparatus in the second hole; e. conjoining the bases of the drill holes.
 2. The method and subsequent steps of claim 1 to effect the recovery of soluble minerals in the ore body by deflecting an initial drill hole horizontally.
 3. A process as claimed in claim 1 in which signalling devices are placed in drill holes.
 4. A process as claimed in claim 1 in which the position of a second drill hole is located by surveying in the position of the signalling device located in an initial drill hole.
 5. A process as claimed in claim 1 in which signalling devices are used to effect the interconnection of drill holes.
 6. A process as claimed in claim 1 in which monitoring-while-drilling equipment is employed to locate or assist in guiding the said signalling devices.
 7. A process as claimed in claim 1 in which subsequent drill holes are conjoined with the initial drill holes.
 8. A process as claimed in claim 1 in which soluble ore is recovered from deep, thick or shallow, thin ore zones.
 9. A process as claimed in claim 1 in which a corridor cavity, a triangular cavity, a square cavity or a rectangular cavity is created to effect the recovery of soluble ore.
 10. A process as claimed in claim 1 to solution mine from drill holes located at the surface a distance of 2,000 to 5,000 feet or more apart.
 11. A process as claimed in claim 1 in which a drill bit and deflecting motor of a different size are attached to the drilling apparatus after the size of the drill hole is reduced by casing.
 12. A process as claimed in claim 1 in which drilling apparatus is pulled from a drill hole to attach a signalling device.
 13. A process as claimed in claim 1 in which a signalling device is encased in a non-magnetic section of drilling apparatus.
 14. A process as claimed in claim 1 in which the direction of fluid in an ore cavity is alternated between two drill holes.
 15. A process as claimed in claim 1 in which the fluid level in an ore cavity is adjusted to control the size and shape of the said ore cavity.
 16. A process as claimed in claim 1 in which the fluid level in an ore cavity is controlled to improve the quality of the effluent.
 17. A process as claimed in claim 1 in which an up-dip drill hole is the influent hole and a down-dip drill hole is the effluent or production hole.
 18. A process as claimed in claim 1 in which a signalling device is propelled to the base of a drill hole by using air or water as a circulation medium.
 19. A process as claimed in claim 1 in which soluble ore can be recovered from dipping ore zones and/or ore zones at different depths, separately or concurrently. 